2001 Q45 Reappearing Check Engine Light

I have a 2001 Infiniti Q45 and had a 1997 prior due to my love for the performance of this beauty. My dilemma now is the check engine light keeps coming back on after having the vehicle serviced. The latest diagnosis turned up something with regard to P1447-Manufacture control, P1492-Auxiliary emission control and P0330-Knock sensor circuit malfunction. Very confused and only wish to have the problem resolved whatever it is once and for all. Please help... Thanks for any suggestions!